Figure 8-10.--Internal gear pump.
Figure 8-8.--Spur tooth pump.
Gear pumps used in support equipment hydraulic
systems are normally driven by electric motors or
through gearboxes by gasoline or diesel engines. Gear
pumps are described in detail in Fluid Power,
LOBE PUMPS.--Another type of gear pump
used in a variety of hydraulic systems is called a lobe
pump (fig. 8-9). The principle of operation of this
pump is exactly the same as the spur tooth pump. The
lobes are constructed so there is a continuous seal
(vane) at the point of juncture at the center of the pump
and also on the housing.
INTERNAL GEAR PUMPS.--Another
common style is the internal gear pump, shown in
fi g u r e 8 - 1 0 . T h i s p u m p c o n s i s t s o f a p a i r o f
gear-shaped elements (one within the other) located in
the pump chamber. The inner gear is connected to the
drive shaft of the source of power. In figure 8-10, you
are shown both the front and the back of the
mechanism. Figure 8-11 illustrates the operation of
In figure 8-11, the teeth of the inner gear and the
spaces between the teeth of the outer gear are
Figure 8-11.--Principles of operation of the internal gear
Figure 8-9.--Lobe pump.